1. Field of the Invention
This invention relates to a network, such as LAN (Local Area Network), which uses a time division multiplexing control communication channel and a contention control communication channel. This invention relates to, for example, the multiplexing bus system network which includes both a time division multiplexing control bus and a contention control bus and is suitable for the multimedia data transmission, and more particularly relates to a multiplexing bus system network which excludes waste of the time slot on the time division multiplexing bus and improves the channel utilization. This invention also relates to, for example, a wireless network which uses both a wireless communication channel employing the time division multiplexing control method and a wireless communication channel employing contention control method, more particularly relates to a wireless network which excludes waste of the time slot of the time division multiplexing channel and improves the channel utilization.
2. Description of the Related Art
FIG. 13 shows a conventional art disclosed in Japanese Patent Laid-Open No. Hei 3-270432. This figure includes a first bus 101 employing the CSMA/CD (carrier sense multiple access/collision detection), which is a kind of the contention control protocol, a second bus 102 employing the time division multiple access protocol (TDMA). Each station 103 is connected with both buses. A central control unit 104 conducts the time division control. The station 103 transmits an access request to the central control unit 104 via the first bus 101. The central control unit 104 conducts the time division control by sending out a time slot control token onto the second bus 102. This configuration has merit that the time division multiplexing control bus can be used under the multimedia processing environment, which needs to transmit a great deal of sound or image data in real time.
FIG. 14 shows a conventional art that two buses in FIG. 13 are conducted by the wavelength multiplexing. In this figure, wavelengths .lambda.1 and .lambda.2 correspond to the first and second buses, respectively. This conventional art is disclosed in Japanese Patent Laid-Open Hei. 2-162939 (U.S. Pat. No. 5,144,466) or Japanese Patent Laid-Open Hei. 5-14385.
In the conventional art, the time slot of the time division multiplexing control is constant. Therefore, if the station to which the time slot is allotted has no transmission request at the time, waste of the time slot degrades the communication efficiency of the whole system. Further, the conventional art does not describe any control systems for the multicast transmission, which plural stations receive a packet.